Labour leader David Shearer says the $50,000-plus New York bank account he failed to disclose to Parliament for three years contained savings from his time as a United Nations employee.

Shearer said he declared the income for tax purposes, but cannot explain his parliament-disclosure lapse.

His pay at the UN had gone into the Chase bank account.

"Those were my savings," he told TV3's Firstline.

He said he was "appalled" when he realised his mistake as he was preparing his latest tax return and had since corrected the record in Parliament's register of pecuniary interests going back three years.

He told reporters yesterday: "I understand people are obviously bemused by it. I have no excuse."

But he has rejected ACT leader John Banks' description of it as a "secret" bank account.

Shearer had been highly critical of Banks' memory lapses during the Kim Dotcom saga, which included him forgetting a helicopter ride to the Megaupload founder's Auckland mansion.

Banks has now attempted to turn the tables, saying Shearer was being hypocritical given his early attacks.

"He set the very high standard for all of us," Banks said, adding that Shearer must be hiding something.

Banks called on Shearer to say exactly where the money came from, how it got there and why he forgot.

Shearer told Fairfax Media yesterday there was no advantage to having the account and there was "nothing special about it".

Asked what that said about his financial expertise, given low interest rates in the US and the exchange rate losses he may have suffered from a rising New Zealand dollar, he shrugged and said: "The bottom line is it is there, and I have nothing more to say about it really."

Banks today also questioned why Shearer would keep such a large amount of money in an account that paid such low interest - maybe 1.5 per cent - when he could earn more in New Zealand.

Shearer had also disclosed a mortgage in the register, which would charge a higher interest rate than the banks paid on deposits in New York.

"Why doesn't he transfer some across and pay off his mortgage?" Banks asked.

Shearer has refused to name the amount in the account, saying that is a matter for him and his family.